Relay



June 22, 1948- c. v. BULLEN Erm. 2,443,784

x\\nir VENTORS Clark Bullen o Carl J. Anderson BY WML, CMM, 07

. Arr :ys

Patented June 22, 1948 RELAY Clark V. Bullen and Carl J. Anderson, Rockford, Ill., assignors to Barber-Coleman Company, Rockford, Ill., a corporation of Illinois i Application May 17, 1943, Serial No. 487,244

The invention relates to relays and, in most aspects, more particularly to polarized relays.

The general object of the invention is to provide a relay which is small in size, light in weight, very rugged in construction and extremely sensitive to changes of its energizing current, but comparatively insensitive to vibration.

Another object is to provide a relay embodying a novel armature and contact support assembly which is balanced in such manner as to contribute materially to the sensitivity of the device.

Another object is to provide a relay having an armature pivotally mounted intermediate its ends in a novel manner and substantially free of external friction.

Another object of the invention is'to provide a polarized relay having a balanced armature and contact support assembly, together with a cooperating adjustable shunt arrangement on the stator of the relay for adjusting the amount of ux passing from stator to armature in order to correlate the same accurately in effecting the initial balance of said assembly.

Another object of the invention is to provide a novel polarized relay embodying a stator presenting pairs of opposed pole pieces at opposite ends of an armature and coacting therewith to produce a high degree of sensitivity of operation within the confines of an extremely compact structure.

Still another object is to provide a relay embodying a novel arrangement and assembly of the parts by means of which the forms of the individual parts are simplified, accurate location relative to each other made easy during manufacture, and a rugged final structure assured.

Further objects and advantages of the invention will become apparent as the following description proceeds, taken in connection with the accompanying drawing in which Figure 1 is an end elevation of a polarized relay embodying the present invention, the casing cover and a portion of the base being shown in transverse section in order to expose the interior arrangement oi the parts.

Fig, 2 is an enlarged transverse sectional view taken substantially along the line 2-2 in Fig. 1.

Fig. 3 is an enlarged fragmentary perspective view of the basic elements of the stator, together with the armature, the other parts being removed.

Fig. 4 is a longitudinal sectional view taken substantially along the line 4-4 in Fig. 2.

Fig. 5 is an exploded perspective view of the componentparts of the armature and contactsupport assembly for the relay.

While the invention is susceptible of various modifications and alternative constructions, we have shown in the drawing and will herein describe in detail the preferred embodiment, but

21 Claims. (Cl. 200-93) it is to be understood that we do not thereby intend to limit the invention to the specific form disclosed, but intend to cover all modifications and alternative constructions falling within the spirit and scope of the invention as expressed in the appended claims.

In the instant exemplication, the invention has been shown as embodied in a direct current polarized relay. This relay comprises switch mechanisms shown as two normally open pairs of contacts although, 'of course, the contacts may be either normally open or normally closed as the requirements of the particular circuit with which they are used may dictate. The illustrated switch contact arrangement includes ilrst and second stationary contacts I0, I I (Flg..2) which are alternately closed by respective movable contacts I2, I3, the latter being moved by a suitable armature or vane I4. The actuating arrangement for selectively opening and closing the switch contacts comprises, as its principal elements, the armature I4 together with a stator designated generally as I5. One of these elements (in the instant construction, the stator) is permanently magnetized, and the other element (herein, the armature) is temporarily magnetized by energization of a suitable operating or control winding, shown as I6. The direction of current ow in the winding determines the polarity of the temporarily magnetized element, relative to the fixed polarity of the other or permanently magnetized element, and thus determines the direction of resultant movement of the armature. As more particularly described hereinafter, current flow in one direction in the winding I6 causes the armature I4 to turn counterclockwise (as viewed in Fig. 2) closing contacts lll, I2, whereas current owing in the opposite direction causes the armature to tilt clockwise to close the other pair of contacts II, i3. When the iiow of current is interrupted, the armature occupies the central or mid-position shown in which position both sets of contacts are, in the present instance, open. Suitable controlled circuits (not shown) may be connected to the alternately operated sets of switch contacts in any desired manner.

it will of course be appreciated that two windings instead of one as shown may be employed and controlled by separate circuits so that the resultant ilow of current in the two windings will determine the armature motion. In such a case, the armature would be disposed in the mid-position when the effects of the currents flowing in the two windings neutralize each other.

Turning now to the details of the individual elements of the exemplary device, the construction of the stator I5 will first be considered (see F18. 3). It comprises a pair of permanent magnets i1, I8 of rectangular or block form which are preferably made oi magnetic alloy including aluminum, nickel and cobalt which is characterized by its high degree of magnetic retentivity. These blocks I1, I8 act, in a structural sense, as spacers between top and bottom members or bridges I3, 20. The latter are made of ferromagnetic material and are clamped against the opposite ends of the blocks I1, I3 by throughfasteners or screws 2i (see also Fig. 4) which extend through grooves on the inner faces of the blocks. Two pole pieces in the form oi integral ears or projections are provided on each of the members I9, 20 and areL bent toward each other to form two spaced pairs of opposed pole pieces. Thus there are projections or pole pieces 22, 23 on the upper member I9 and projections or pole pieces 24, 25 on the lowery member 20. The projections 22, 24 extend toward each other with a small air gap between their opposed ends to form one of the cooperating pairs of pole pieces, while the projections 23, 25 are similarly arranged to form a second pair spaced from the first. The permanent magnet blocks I1, I8 are arranged with their ends of like polarity extending in the same direction. For example, the upper ends may both be north poles and the lower ends south poles, in which case both of the upper pole pieces 22, '23 will be north poles and both of the lower pole pieces 24, 25 will be south poles (all as indicated by the letters N and S in Fig. 3).

The basic statorstructure just described provides a rigid mounting for the stationary switch contacts I and II which mounting greatly facilitates the establishment and maintenance of accurate contact spacing. For this purpose, L- shaped brackets 26 are secured rigidly, as by spot welding, to the outer faces of the lower pole pieces 24, 25 and their horizontal arms 2Gb are apertured to receive shouldered insulating bushings 28. Studs 21 project upwardly through these bushings and the contacts I0 and II are threaded into enlargements 29 on the studs. The lower ends of the studs are riveted to the bushings and brackets. Terminal strips 30 are fixed to the lower ends of the studs 21 for connection of the same to suitable controlled circuits (not shown). As shown in Fig. 2, the spacing between the fixed and movable electrical contacts I0, Il, I2, I3 is adjustably limited so that closing of the contacts substantially prevents yany further movement of the armature toward the pole faces. This has the advantage of eliminating clinging due to residual magnetism and facilitates thereturn of the armature to the central position upon deenergizing the Winding I6.

The portions of the brackets 26l fixed to the outer faces of the pole pieces 24, 25 extend for the full width of the latter so that they substantially double the end face areas of these pole pieces thereby improving the stability of the magnets and increasing the sensitivity of the relay. 1To match this enlarged area, additional blocks 23a are spot welded to the outer faces of the opposed upper pole pieces 22, 23.

Screws 3|a. pass through holes in a supporting base 3|' and thread into the lower bridge member 2li to x the stator in place on the base. Enclosure of the device is completed by a removable cover 32 of inverted cup shape telescoped down over the unit and fitted in a groove along the edge of the base. Upon reference to Fig. 2, it will be seen that the terminals 30 for the stationary contacts l0, II project downward through suitable apertures 33 in the base. Both the base and cover are desirably made of insulating materia'l-such as molded plastic.

The armature I4 is of generally rectangular plate-like form, being made oi ferromagnetic material such as soft iron, and in the present instance is dimensioned to extend within the air gaps between both of the pairs oi opposed pole pieces 22, 24 and 23, 25 (Figs. 2 and` 3). The air gaps are sufficiently wider than the thickness of the amature as to permit the tilting or pivotal movement of the latter about a central transverse axis thereof requisite for shifting the movable contacts I2, I3.into and out of closed position. The ends of the armature I4 are substantially equal in width to the width of the cooperating pole pieces, 'but the central portion of the armature- I4 is reduced in cross-section to only a small fraction of that of its end portions. For this purpose a hole 34 and side notches 35 are formed in the central portion of the armature (Fig. 5). This reduction of cross-section of the amature intermediate its ends limits the amount of flux which can pass through it. Accordingly, even though an excessive amount of current should be applied to the operating winding I6, the iiux density in the end portions of the'armature is strictly limited by the saturation point oi the much smaller central portion, so that permanent magnetization of the armature, even under adverse conditions, is positively precluded. Permanent magnetization of the armature should be avoided since if it should take place, the armature would fail to return to its central or neutral position upon discontinuance of the energizing current in the winding I6.

Of particular importance in the relay is the arrangement for supporting the armature I4 and the movable contacts I2, I3. As illustrated, this comprises a. carrier in the form of a one-piece, resilient, sheet metal stamping, designated generally as 36( Fig. 5) and made of electrically conductive but non-magnetic material, preferably beryllium copper. The armature I4 is ilxed to the underside of the stamping 36 by rivets 31. Both the armature I4 and stamping 36 are substantial- 'ly symmetrical about a transverse central axis at A-A and about which the assembly tilts or pivots so that for the angle oi rotation permitted the assembly is substantially balanced both statically and dynamically relative to its pivotal axis.

Instead of pivoting the armature for movement about its central transverse axis by ordinary bearing pivots, thin and torsionally flexible lateral projections or spring pivots 36a are preferably provided in the stamping 36 itself to extend from the central portion of .the latter as shown. These projections 36a. have sufiicient torsional flexibility as to lpermit the necessary tilting of the armature and contact support assembly about the axis A-A for opening and closing the contact points. The projections 36a are bent downward and their outer ends there terminate in elongated supporting elements or bridges 36h which are clamped between the opposed end faces oi the pole pieces (see Figs. 2 and 4). Also constituting part of the stamping 36 are elongated and oppositely extending contact fingers 36e to the outer ends of which are fixed the contact points I2, I3. These contact fingers 36o are symmetrical with respect to each other about the axis A--A so that all movable parts of the mechanism, namely, .the armature I4 and contact ngers 36.0, are ln dynamic balance about their axis of movement AA. This contributes very materially to the sensitivity and precision of operation of the relay while reducing to a minimum the response of the armature to vibration of the relay mounting.

, Not only is a nice, balance of .the movable parts achieved by the construction described above, but in addition the use of the torsionally-ilexible, resilient projections 36a for pivoting the movable parts contributes to the precision of operation of the device. In the iirst place, such an arrangement Iinsures a yieldable resistance .to movement of the moving parts which remains constant with time as distinguished from the variations or resistance that are likely to ibe encountered in ordinary bearing arrangements due to inevitable changes in frictional resistance. The illustrated mounting alsoobvlates the necessity of separate centering springs or the like, since the extensions 36a are suillclently resilient themselves yto bias the assembly constantly, though yieldably, to its central position. The low cost of the arrangement is manifest, and, in addition, such a supporting arrangement for the movable assembly is especially resistant to interference by external vibratln, shocks and jars.

To locate the amature and contactsupport assembly accurately with reference to .the stator, thesupporting elements 36h are notched at their ends (Figs. 2 and 5) .to form locating shoulders 36d abutting the end portions of the pole pieces 24, 25. In assembling .the device, the stamping 36, with armature IIIy attached, is dropped into place on the pole pieces 24, 25. The upper stator member I9 is subsequently secured in place, thus clamping the end portions of .the members 36h in position. The locating shoulders on .the latter members 36b determine the position of the stamping 36 relative to the pole pieces 24, 25 so that the contacts I2, I3 carried by .the fingers 36c are accurately located relative to .these pole pieces. The cooperating stationary contacts I9, II are, as heretofore noted, carried by brackets which are rigid with these same .pole pieces 24, 25. It follows, therefore, .that when the parts are placed in an assembly jig and put .together in the manner indicated, that the cooperating pairs of contacts will be accurately aligned with each other, using the -pole pieces 24, 25 as reference points. This substantially simplies the problem of precise alignment of the contact points in a manner to insure that .the full faces of the points will meet accurately as they open and close in the operation of ythe device. Such alignment is requisite to assure against uneven wear. excessive contact resistance and arcing.

Means is provided for permitting adjustment of the polarizing flux to permit the attainment of precise balance of the magnetic forces acting on the armature and contact-support assembly and to cause the armature to remain stably in the central or null position. While this adjustment may be effected in various ways, it is accomplished in the present instance by a magnetic shunt arrangement. As shown in Figs. 1 and 2, the shunt is in the form of a strip 38 of ferromagnetic material pivoted to the outer face of the pole piece block 26a by a screw 39. As shown in Fig. 1 the shunt is sufficiently long that the lower end portion thereof may overlap and be in contact with the outer face of the corresponding lower pole piece. The center portion of the shunt 33 is bent outwardly to clear the gap between the ends 'of the pole pieces and alsoto cause the lower end of the shunt to be resiliently pressed against the underlying face of the pole piece. By swinging the shunt 38 about its pivot 39 the amount of overlap oi. the shunt with respect to the lower pole piece can be varied, thus adjusting the amount of ux which is by-passed through the shunt and around the' end of the armature and the air gap between it and the pole pieces 22 and 24.' A similar shunt is provided on the pair of pole pieces at the opposite end of the armature also serving to shunt,` or in other words by-pass, a portion of the magnetic flux and thereby reduce the flux ln the gap. The polarizing ux applied to opposite ends of the armature can thus be adjusted individually in setting up a precise balance of the armature.

Through the use of a plurality of shunts associated with the respective pairs of pole pieces 24 and 26, it is possible to vary the value of the magnetic potential at any pole piece relative to the value oi' the potential at the other pole piece oi the same polarity. In this way the relative values of the magnetic potentials at opposite ends of the armature may be equalized or changed in either direction in order to compensate for the variations in the magnetic and mechanical forces acting on the armature when the operating winding is inactive. Therefore, the armature may be balanced precisely in spite of force variations that are inherent due to non-uniformity in materials, relative spacing of the armature and pole faces, pole face size variations, etc.

Not only the armature and contact-'supporting assembly, but also the operating winding I6 is clamped in place by the opposed stator members I9 and 29. Upon reference to Figs. 2 and 4 it will be seen that the winding I6 is coiled on a spool comprising a lcore 40 and end members 4I. The end members 4I are generally rectangular in shape and are dimensioned to be clamped tightly between the stator members I9, 20. The core 40 is suiliciently large in interior dimensions that it loosely encircles the armature and contact-support assembly with adequate clearance for free movement of the latter. Terminals 42 for the winding I6 (see Fig. 1) are xed to the insulating base 3I and may be connected to any suitable control circuit for energization of the winding.

As to the operation of the relay described, it may be assumed that the polarity of the permanently m-agnetized stator is that indicated in Fig. 3. The operating winding I6 does not appear in Fig. 3 but it is coaxial with the armature I4 and we may first assume that the energizing circuit for the winding is completed in such manner as to cause current to traverse it in the direction of the line of arrows I6a. In such case the ow of iiux induced in the armature I4 will polarize the same with a south pole at its righthand end and `a north pole at the left end. The left or north' pole of the armature is then attracted by the oppositely polarized pole piece 24 and repelled bythe pole piece 22, while the right end of the armature is attracted upward to the pole piece 23 and repelled by the lower pole piece 25. In this way the armature is caused to tilt .in a counterclockwise direction, thereby closing the contacts I0, I2. Since tilting causes the left hand end of the armature (Fig. 2) to be brought into closer proximity with the pole piece 24 (which is a south pole), and the right-hand end to be brought into closer proximity with the pole piece 23 (a north pole), such movement causes a redistribution of the permanent magnet flux, a portion of the ux from pole `piece 23 passing through the armature I4 to enter pole 24. Such' redistribution causes an increase in ux density adjacent the faces of pole pieces 23 and 24 and p produces a displacing torque #MannA a'diminution of flux density adjacent the faces of pole pieces 22 and 25. The latter obviously tending t counteract a portion of the centering torque exerted by the torsion mount.

It will readily be appreciated by those skilled in the art that whether the armature of the relay shown stably seeks a central position depends upon the relative magnitudes of th'e displacing torque mentioned immediately above and the restoring torque of the torsion springs 36a. Only4 when the latter predominates will the armature return to center on Vcutting of! the operating winding'current. Adjustment producing stable centering is preferred for most applications of our relay, its structure being especially suited to the same.

Upon interrupting the energizing current to the winding I8, the armature Il is'immediately deenergized, removing the unbalanced magnetic force due to the current flowing through winding IB, whereupon the restoring force of th'e torsion in the supporting extensions 38a snaps the armature back to its initial or central position. Similarly, when energizing current is fed through the winding I6 in a direction opposite to that indicated by the line of arrows Ita, the armature I4 is temporarily magnetized with a polarity opposite to that described above, whereupon it tilts in a clockwise direction, closing the other pair of contacts I I, I3. The line degree of dynamic balance of the device and the fine degree of magnetic adjustment provided by the shunts render it so sensitive that only very small current need be applied to the winding I6 in order to actuate the armature.l

Suitable controlled circuits (not shown) may be connected to the alternatively operated sets of contacts IIl, I2 and II, I3. Connections are made to the stationary contacts III. II through their terminals 30 while the movable contacts I2, I3 are `connected to a common circuit. As to the latter, it will be noted that the movable contacts are interconnected through the electrically conductive stamping 36 and this is in turn in contact with the metal stator structure I so that a lead wire (not shown) may conveniently be attached to the latter for establishing a circuit to the movable contacts. All other terminals are insulated from the stator as heretofore described.

From the foregoing it will be seen that a relay has been provided which is capable of extreme sensitivity of operation, due to the dynamic balance of its moving parts, the close coupling of its magnetic circuits, and possibly other factors. On the other hand, the device is small and extremely compact and is little affected by external vibration or shock. The overall cost of the device is low because of the simplicity of its parts and also because the device is comparatively easy to assemble While still retaining accurate location of the relatively movable parts. As to assembly,v it will be' n oted that only two screws 2I are required to secure the various component parts of the mechanism in assembled relation. -By mounting the stationary contacts independently of the base 3i and directly on the rigid stator structure insteadof the base 3i, accurate spacing of the fixed and movable contacts is maintained irrespective ofirregularities or changes in the shape of the base.A

Some further comment on the theory of operation'of the magnetic shunts 38 may be useful to those skilled in the art. As previously noted, the shunts may be adjusted to vary the magnetic potentials at opposite ends oi the amature to balance the armature precisely in its mid position. Moreover, adjustment o! the shunts appears to have an eifect on sensitivity of the relay. As to theory of the latter eiect. what apparently happens is that adjustment of the shunts not only varies the magnetic potentials at the armature ends but also varies the ux density in the air gaps. l y

The latter variation seems to directly ailect the sensitivity, a greater sensitivity being imparted with increase in flux density up until instability occurs.

Simply by way of example, one of the various adjustment procedures that may b e used for the shunts 38 (Fig. 1), includes reducing the sensitivity by rotating the shunts 3l to a positionl well down on the permanent magnets, raising one of the shunts or the other as required to place the armature in acentral or of! position, then raising the shunts at each end of the two air gaps simultaneously to an extent just suillcient to enable the armature to remain stably in the central position. If it is desired that the relay operate on a. predetermined minimum current, the shunts are raised simultaneously only to the extent required t'o produce the desired sensitivity.-

We claim as our invention:

1. In a relay, the combination of a ferromagnetic stator presenting a generally rectangular pole piece, an armature disposed substantially at right angles to the end of said pole piece and withone end -of the armature lying closely adjacent the end of the pole piece for passage of flux therebetween, a carrier for..said armature comprising a, pair of side members extending along opposite sides of the armature and having notched portions engaging the end of said pole piece for accurately locating the armature relative thereto, a contact finger fixed to said armature and movable therewith, a first switch contact on said contact finger, a cooperating second switch contact, and means' including a bracket rigid with a side face of said pole piece for accui rately locating said second contact relative to said pole piece, whereby both said first and second contacts are accurately located relative to said pole piece as a reference point and thereby accurately located with respect to each other.

2. A polarized relay comprising, in combination, a stator element and an armature element each made of ferromagnetic material, said\stator element presenting two spaced pole pieces and said armature extending between said pole pieces with its ends in proximity to the latter, one of said elements being permanently magnetized and the other being equipped with an operating winding for temporarily magnetizing the same with a desiredpolarity, and a non-magnetic member l fixed to said armature and presenting torsionally-iiexible lateral projections having their outer ends bent substantially at right angles and terminating in elongated bridge elements arranged to span the distance between and rest upon said pole'pieces of the stator, said bridge elementsy being notched at their ends to present shoulders facing endwise of such elements and adapted to abut against the side faces of said pole pieces for accurate location of said armature with reierence to said pole pieces in a direction longitudinal of the armature.

'said armature extending between said pole pieces with its ends in proximity to the latter, one oi' said elements being permanently magnetized and the other being equipped with an operating winding for temporarily magnetizing the same with a desired polarity, a one-piece stamping of nonmagnetic sheet metal xed to said armature and presenting laterally-extending torsionally-ilexible projections terminating in bridge elements arranged with their opposite ends resting on and supported by said pole pieces of the stator, said sheet metal stamping also including a pair of projecting integral contact ngers arranged substantially at right angles to said projections, and stationary contacts disposed for coaction with respective ones of said contact ilngers.

' 4. In a relay, the combination of an armature, a thin sheet of flexible material having a, central portion secured to said armature, iianges along opposite margins and narrow integral connections lying in the plane of said sheet between said central portion and said flanges, said anges being disposed at right angles to the plane oi said sheet and said connections, and means rigidly supporting said flanges.

5. In a device of the type described, the combination of, a, generally iiat armature, a thin sheet of iiexible non-magnetic material having a central portion secured to said armature and oppositeiy projecting ribbon-like extensions intermediate the ends of said armature, and non-magnetic flanges disposed along opposite sides of said armature in planes normal to the armature and connected intermediate their ends to the outer ends of said extensions whereby the latter` provide the sole support for said armature and serve to torsionally bias said armature into a normal position with respect to said flanges.

6. In a device of the type described, the combination of two spaced pairs of pole pieces having opposed faces dening two air gaps lying in a common plane, an armature dimensioned to extend substantially from one of said gaps to the other, non-magnetic bars disposed on opposite sides of said armature with their opposite ends projecting between the ends of said pole pieces and supported thereby, and a non-magnetic sheet member secured to said armature and having resilient projections on opposite sides disposed intermediate the ends of the armature, said projections being secured at their outer ends to said bars and torsionally iiexible to permit pivoting of the armature and to urge the latter toward a balanced position.

7. In a device of the type described, the combination of two spaced pairs of pole pieces having opposed parallel and flat faces deiining two air gaps, an armature dimensioned to extend substantially from one of said gaps to the other, nonmagn-etic bars disposed on opposite sides of said armature with their opposite ends projecting between the ends of said pole pieces andsupported thereby, shoulders on said ends abutting against the sides of said pole pieces to hold the bars against endwise movement, and a non-magnetic member secured to said armature and having resilient projections on opposite sides disposed intermedate the ends of the armature, said projections being secured to said bars and torsionally flexible to permit pivoting of the armature.

8. A device of the type described comprising, in combination, two spaced pairs of pole pieces having opposed faces defining two air gaps lying in a common plane, means permanently magnetizing the pieces on one side of said gaps of one polarity and the pieces on the opposite side of the gaps of the opposite polarityan amature spanning the pairs of pieces with its opposite ends disposed in said gaps, means supporting said armature to turn about an axis disposed midway between said gaps and in the plane of the latter, and a plurality of shunts respectively operable to by-pass magnetic iiux around the respective air gaps and individually adjustable to vary in opposite Adirections the magnetic potential at one of said pole pieces relative to the magnetic potential at the pole piece of the same polarity in the other of said pairs.

9. A device of the type described comprising, in combination, two spaced pairs of pole pieces having opposed races dening two air gaps lying in a common plane, means permanently magnetizing the pieces on one side of said gaps of one polarity and the pieces on the opposite side of the gaps of the opposite polarity, an armature spanning the pairs of pieces with itsopposite ends disposed in said gaps, means supporting said armature to turn about a central axis and resiliently holding the armature spaced substantially equidistant from the pole faces on one side of the armature, and shunting means adjustable to bypass a portion of the magnetic iiux around at least one of said air gaps and compensate for lack of complete symmetry in the circuit for the magnetic flux through said two air gaps and variations in the mechanical forces acting on the armature whereby the latter is normally held in balanced position.

10. A device of the type described comprising, in combination, a pair of alined, pole pieces having opposed parallel faces defining an air gap, a second similar pair of pole pieces having faces deiining a second air gap and respectively disposed in the planes of said iirst faces, means permanently magnetizing the pieces on one side of said gaps of one polarity and the pieces on the opposite side of the gaps of the opposite polarity, an armature spanning the pairs of pieces with its opposite ends disposed in said gaps, means supporting said armature to turn about an axis disposed midway between said gaps and in the plane of the latter, and means for shunting flux around one of said gaps and selectively adjustable to vary the relative magnetic potentials at least at one of said pole pieces relative to the potentials of the other pole pieces.

11. A device of the type described having, in combination, a pair of iiat bars of ferromagnetic material disposed in spaced parallel relation and having projections integral with the bars on opposite sides and intermediate their ends, the projections on each bar being bent into parallelism with each other and into longitudinal alinement with the projections on the other bar, blocks disposed between and abutting against the two bars at the ends thereof and spacing the latter with the end faces of the alined projections spaced from each other, at least one of said blocks being composed of ferromagnetic material and permanently magnetized to cause a continuous ow of flux through the two air gaps defined by said faces, and through bolts arranged longitudinally adjacent the inner sides of said blocks respectively for connecting the ends of said bars and clamping said blocks between the bars.

12. A polarized relay comprising, in combination, an actuating winding having an axially extending opening therein, a polarizing structure of generally boxlike form enclosing said Winding and presenting pairs of permanent magnet pole pieces of opposed polarity at the respective ends 4respective ones of said pole pieces, said assembly also including bridge members extending in parallelism along opposite side edges of said armature ,and supported at their opposite ends by said pole pieces, said bridge members being joined to said armature by torsionally ilexible integral projections on'said bridge members located on said.

transverse axis of symmetry, whereby said armature is supported for tilting about such axis, and switch means at opposite ends of said armature adapted to be actuated thereby and including contact ngers carried by said armature in position to project axially from its opposite ends and shaped symmetrically with reference to each other about said transverse axis of symmetry.

13. A polarized relay comprising, in combination, an actuating winding having an axially extending opening therein, a polarizing4 structure of generally boxlike form enclosing said winding and presenting pairs of permanentmagnet pole pieces of opposed polarity at the respective ends of said opening with the central longitudinal axis of said winding passing substantially through the centers of the gaps between the opposed ends of said pairs of pole pieces at the opposite ends of said winding, a combined contact support and 'armature assembly extending axially through said opening and having a transverse axis of symmetry passing substantially through the center of said winding, said assembly including an elongated flat armature extending axially through said opening and projecting equal distances from opposite ends of said winding into said gaps between respective ones of said pole pieces, said assembly also including bridge members extending in parallelism along opposite side edges of said armature and supported at their opposite ends by said pole pieces, means supporting said armature on said bridge members for tilting motion of the armature about said transverse axis of symmetry, and switch means at opposite ends of said armature adapted to be actuated thereby and including contact ngers carried by said armature in position to project axially from its opposite ends andshaped symmetrically with reference to each other about said transverse axis of symmetry.

. 14. The combination with a permanently magnetized stator structure presenting two pairs of opposed and opposite polarity pole pieces, and an armature extending into proximity with the gaps between both of said pairs of pole pieces and mounted to rock about a transverse axis mid- `waybetween said gaps, said armature having associated therewith means including an actuating winding for oppositely polarizing the portions of said armature presented to respective ones oi said gaps, oi' means for adjustably varying the total ilux threading between one of said pairs of pole A pieces and through said armature relative to the total of ilux threading between the other of said pairs and through said armature, whereby said 12 Y last-mentioned means lmay be adjusted to balance the tractive forces applied to said armature by ilux from said pole pieces tending to rock said armature about said axis..

15. In a device of the type described, the combination oi a statorY structure presenting two pairs of spaced pole pieces defining two air gaps lying in a common plane, the portion oi said structure lying on one side of said plane being permanently magnetized with one polarity and that on the other side with opposite polarity, an armature spanning the pairs of pole pieces with its opposite ends disposed in close proximity to said gaps. means supporting said amature to turn about an axis disposed midway between said gaps and in the plane ot the latter, and shunts comprising strips of magnetically permeable metal pivotally mounted on respective pole pieces or each of saidpairs of the latter and positioned to contact a portion ofsaid structure lying on the opposite side of said plane iromthe pieces 'to which they are pivoted.

16. The combination with a permanently magnetized stator structure presenting two pairs of opposed and opposite polarity pole pieces, and an armature extending into proximity with the gaps between both of said pairs of pole pieces and mounted to rock about a transverse axis midway between said gaps, said armature having associated therewith means including an actuating winding for oppositely polarizing the vportions of said armature presented to respective ones of said gaps, of means individually associated with the respective gaps and operable selectively for varying the magnetic potential in each end of said armature relative to that at the other end.

17. The combination with a permanently magnetized stator structure presenting two pairs oi opposed and opposite polarity pole pieces, and an armature extending into proximity with the gaps between both oi said pairs of pole pieces and mounted to rock about a transverse axis midway between said gaps, said armature having associated therewith means including an actuating winding for oppositely polarizing the portions of said armature presented to respective ones of said gaps, of means associated with said pole pieces for varying the magneticlpotential in each end of said armature relatively to that at the other end but for also varying the iiux densities in respective ones of said gaps.

18. In an electromagnetic device, the combination comprising: a pair of pole pieces having op- I v larity tc said faces and forming a magnetic circuit therewith, a magneticallyV permeable vane having a ilrst end portion in said gap, said vane being pivoted for 'movement within said gap substantially normally to said pole faces, spring pivot means biasing said vane substantially centrally in said gap, said vane having a second end portion coupled to said magnetic circuit, a winding surrounding said vane intermediate said end portionsyilrst magnetic shunting means associating at least one of said pole pieces with said magnetic circuit for adjusting the magnetic potential at the center of said gap, second magnetic shunting associated with another pole piece for bypassing ilux in aselected portion of said magnetic circuit foradjusting the potential at said second end portion of said vane whereby the potential at the ends of said vane may be equalized under zero current conditions while maintaining the flux density Within said gap Vat a predetermined magnitude.

19. In an electromagnetic device, the combination comprising: a pair of pole pieces having opposed faces deiining a narrow air gap, a permanent magnet applying magnetism of unlike polarity to said faces and forming a magnetic circuit therewith, a magnetically permeable vane having a iirst end portion in said gap, said vane being pivoted for movement within said gap substantially normally to said pole faces, spring pivot means biasing said vane substantially centrally in said gap, said vane having a second end portion coupled to said magnetic circuit, a winding surrounding said vane intermediate said end portions, and means providing a plurality of separate flux shunting paths for adjusting individually the magnetic potentials at the center of said gap and at said other end of said vane as well as for varying the ux density in said gap.

' 20. In an electromagnetic device, the combination comprising: iirst and second pairs of magnetic pole piecesl said pairs including pole pieces of unlike polarity separated by an air gap, a permanent magnet applying magnetomotive force across the gaps formed by associated poles, a strip of magnetically permeable material pivoted at its central portion and having ends projecting respectively into said gaps, a torsional support tor pivoting said magnetic strip, said torsional support biasing said strip into a normal position centered thin said gaps, the polarity of said pole pieces and the orientation of said torsional support enabling movement of the ends of said armature toward pole pieces of unlike polarity respectively, a winding surrounding said strip for setting up a flux therein, a' magnetic shunt, and means supporting said shunt to span between one of said pole pieces and said magnet with said shunt pivoted on one and in frictional sliding contact with the other' tovary the magnetic potential existing in such pole piece.

21. In an electromagnetic device, the combination comprising: a pair of pole pieces having opposed Iaces deiinlng a narrow air gap, a. permanent magnet applying magnetism of unlike polarity to said faces and forming a magnetic circuit therewith, a magnetically permeable vane having a rst end portion in said gap, said vane being plvoted for movement within said gap substantially normally tov said pole faces, spring pivot means biasing said vane substantially centrally in said gap. means including electrical contacts for limiting the range of movement of said vane 14 in either direction in said gap, said vane having a second end portion coupled to said magnetic circuit, a winding surrounding said vane intermediate said end portions, and means providing a plurality of separate flux shuntingpaths for adjusting the magnetic potentials at the center c! said gap and at said other end of said vane s well as for varying the flux density in said i ap, said shunting means serving to reduce the magnitude of the permanent magnet flux between said pole pieces to a point where'the magnetic attraction between said vane and said pole pieces due solely to permanent magnetism upon deflection of said vane from its central position is slightly less than the restoring force of said biasing means at all positions' within the range of armature movement permitted by said movement limiting means.

CLARK V. BULLEN. CARL J. ANDERSON.

REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PATENTS Number Name Date 281,249 DInfreville July 17, 1883 316,707 Weston Apr. 28, 1885 541,471 Corey June 25, 1895 586,888 Williams July 20, 1897 850,402 Scribner Apr. 16, 1907 987,192 Turbayne Man 21, 1911 1,164,407 Schiessler Dec. 14, 1915 1,237,113 Sparks Aug. 14, 1917 1,263,383 Craft Apr. 23, 1918 1,328,825 Drysdale Jan. 27. 1920 1,333,247 Cummings Mar. 9, 1920 1,562,252 Pihl Nov. 17, 1925 1,448,824 Blakeslee Mar. 20, 1923 1,646,234 Creed Oct. 18, 1927 1,696,170 Leake Dec. 18, 1928 1,719,192 Osborne July 2, 1929 1,814,798 Guedon July 14, 1931 1,893,856 Broughton Jan. 10, 1933 1,922,679 Hammer Aug. 15, 1933 2,051,475 Grandstai! Aug. 18, 1936 2,100,162 Fritz Nov. 23, 1937 2,125,150 Bruns July 26, 1938 2,135,843 Pye Nov. 8, 1938 2,217,406 Hanna Oct. 8, 1940 2,245,511 Turnbull June 10, 1941 2,267,808 Blount Dec. 30, 1941 

